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Lantea is one of only two known planets in its solar system which has an atmosphere capable of sustaining human life. The majority of Lantea's surface area is covered with a large ocean. It has only one, relatively small, continent, covering roughly 15 million square miles.

Life on the planet is threatened by two great dangers. First, every 20 years the ocean gets unusually warm, which causes the development of powerful storms that can cover nearly 20% of the planet and cause great destruction. Another great danger is a Coronal mass ejection of the planet's sun which happens about every 15,000 years, and is capable of destroying all life on the planet. The Ancients formerly prevented this by expanding the shield of the city to cover a great portion of the planet. Nevertheless, the areas unprotected by the shield suffered damage so extreme that it caused the extinction of several species. With Atlantis no longer residing on Lantea, future life on the planet is potentially at risk of mass-extinction. (SGA: "The Storm", "The Eye", "Echoes", "First Strike")

After the Ancients left Earth between 5 and 10 million years ago, they finally settled in the Pegasusgalaxy, being on Lantea for at least 45,000 years. From there, Atlantis was sitting as an island on the water, and the Ancients started to explore their new home galaxy, seeding life on planets and building a whole new network of Stargates, this time using a new design. To protect their new home, the Ancients built a large network of defence satellites stationed all across the Lantean system. To have an alternative power source for their city, the Ancients also built a mobile drilling platform to tap into geothermal energy on the ocean floor.

While exploring the galaxy, the Ancients—which were called the Lanteans in this galaxy—encountered creatures called Iratus bugs. These creatures fed on humans, and the mix of human DNA with Iratus DNA while the bug was going through egg-laying cycles caused mutations in the bugs' offspring. Generations of these mutations resulted in a race called the Wraith, which soon started to take over the galaxy. This started a centuries-long war with the Ancients. During this war, the Wraith sent many ships to Lantea to destroy Atlantis. On their way, they destroyed the whole satellite network, except for one, and attacked the city from orbit. The Ancients repelled the attacks. However, unknown to them, one Wraith cruiser from the first attack wave survived and crash-landed into the ocean, where it lay dormant for more than 10,000 years. Finally, the Ancients submerged Atlantis and left the city for their old home, Earth.

Ten thousand years later, the Atlantis expedition from Earth discovered Atlantis and now inhabits the city. Later the mainland became home to the Athosians, humans from the Pegasus galaxy whom Ancients from the warship Tria—who returned to Atlantis and were subsequently killed by the Asurans—later resettled on another planet.

The Athosian settlement on the main continent of Lantea.

After the humans had controlled the city for about three years, the Asurans attacked Atlantis with a beam weapon through an orbiting satellite with an attached Stargate. The only way to escape this weapon, which could find the city anywhere on the surface, was to use the Stardrive to fly the entire city to another world, where the Asurans would not be able to follow them. Lantea was abandoned with the intended final destination of M12-578 as its new home planet. However, Atlantis was damaged in the attempt and dropped out of hyperspace far from the new planet, with many of the crew hurt and with only 24 hours of power remaining. After a daring heist on Asuras, during which Dr.Elizabeth Weir was captured along with the knowledge of M12-578, Atlantis was flown to another world with a habitable ocean: M35-117, which Dr. Weir did not know about. (SGA: "Rising", "The Defiant One", "Before I Sleep", "The Return, Part 1", "The Return, Part 2", "Submersion", "First Strike", "Adrift", "Lifeline")

Following the decision to return Atlantis to the Pegasus Galaxy, Lantea was once again chosen as the city-ship's new home as it was believed that it was the last place any enemies would look for Atlantis given how long it had been abandoned. However, seven days into the nine day hyperspace journey between Earth and Lantea, Atlantis' hyperdrive broke down and the city was forced to land on a much colder, less habitable planet at the edge of the galaxy instead of Lantea. (SGA: "Legacy: Homecoming")